PCI 6024 E 5V Terminal maximum current

[jecifuentes]

Hi!

I am using the PCI 6024 to read an encoder. This encoder needs maximum a supply current of 85 mA to work. Right now I am connecting it directly to the +5V and GND terminals of my 6024 and it works ok. I want to know the maximum current that this +5V Terminal can supply. I have the "NI 6023E/6024E/6025E Family Specifications" ( http://www.ni.com/pdf/manuals/370719c.pdf ) document with me and there is a table on page 2 that says that the +5V terminal "Source (mA at V)" is "1 A fused"... and on page 9 under "Power Requirement" it says that for +5 VDC (+- 5%) the current is 0.7 A.

I don't know if I am interpreting correctly this information. Does this mean that this +5V Terminal can supply maximum 1 A and that the DAQ needs 0.7 A to work? Or am I misunderstanding the information? Can someone help me please with this information? I want to know if I can connect more encoders to this same terminal without damaging the DAQ.

Thanks!

Jorge

[lfelias]

Hi Jorge,

As you can see in the next link: http://sine.ni.com/nips/cds/view/p/lang/en/nid/10968

Digital I/O
Bidirectional Channels	8
Input-Only Channels	0
Output-Only Channels	0
Number of Channels	0 , 8
Timing	Software
Logic Levels	TTL
Input Current Flow	Sinking , Sourcing
Output Current Flow	Sinking , Sourcing
Programmable Input Filters	No
Supports Programmable Power-Up States?	No
Current Drive Single	24 mA
Current Drive All	192 mA

The maximun current on a single DIO channel is the 24 mA. The power requirements specs are for what the PCI needs to operate.

If you need to power up the encoder with more than 24, what you can do is to use the DIO as parallel current drives to increase the amount of current that you can get from the PCI.

If you notice, the current drive single is 24 mA, but the current drive all is the 192 mA, so you can connect maybe 4 of the DIOs to provide more than 85 mA.

I hope this information is useful.

Regards,

[jecifuentes]

Thank you very much Luis Elias for the information. I am not using the DIO terminals to supply current to my encoders. I am using the +5V terminal of the DAQ. My question is if this +5V terminal (PIN 14 or PIN 😎 can supply enough current for both encoders.

Thanks!

Jorge

[johnsold · Accepted solution]

The 6023E/6024E/6025E Family Specifications indicates that the +5 V terminal is fused at 1 A (Table 1. I/O Terminals, page 2).  So I would not draw more than about 600-700 mA continuous current load or up to about 1 A intermittently, provided that the average current was quite a bit lower.

Lynn

[jecifuentes]

Thank you very much Lynn and Luis Elias for your help! I always have some trouble understanding the data sheets of these devices.

Have a nice day!

Jorge

[johnsold]

Jorge,

Understanding data sheets can sometimes be a challenge, but it is worth the effort to learn how to read and interpret them.  Often a data sheet is the only source of detailed information about a device or product.

I have seen a few which apparently were written by a person with no knowledge of how the device worked, but most of the time the information is valid.

In the case of the available from the +5 V pin you asked a good question.  The pin is provided for exactly the purpose you proposed (although I do not know whether it will work for your encoders). The way NI chose to document this piece of information was not done very well. First, the information was in a separate document from the specifiactiosn for your card. Second, the data was presented in a manner which required specific knowledge and experience to interpret, and that knowledge and experience is not required to apply the device otherwise.  The specification should have appeared as Maximum continuous current from the +5 V pin = xxx mA and maximum peak current <= 1 A. That specification should be in both documents.

Lynn